Abstract
A system for on-line and real time measurement of water flow rate in a plant stem was developed on the basis of stem heat balance simplified by the heat flux control. Heat (Q) supplied from a main heater attached to the stem surface is diffused through heat flux (qf) by water flow in the stem, heat flux (qs) from the surface of the main heater to the surroundings, and upward and downward heat fluxes (qu andqd) by conduction in the stem, that is, Q=qf+qs+qu+qd. In this system, qswas kept constant by controlling Q, andquandqdwere also kept constant by controlling two subheaters attached to upside and downside of the main heater. Thus, change in theQdirectly related to fluctuation ofqf. So, water flow rate in the stem was able to be calculated from the theoretical equation (Eq. (5) ) by usingQand temperature difference (Tu-Td) in the stem between upside and down-side of the main heater. We proposed to call this system “Heat Flux Control method (HFC method) .” From dynamic and static characteristics of the system in a glass tube used as the stem model and in an intact plant, it was estimated that HFC method can be used as a reliable tool for quantitative analysis of water flow in the stem and applied to researches on water process in the plant.
